Stats

Locked Locked
Replies 8
Subscribers 93
Views 17912
Members are here 0

This discussion has been locked.

You can no longer post new replies to this discussion. If you have a question you can start a new discussion

TIE-HI and TIE_LO cells

vedamrit over 13 years ago

Can we use VDD and VSS in place of TIE-HI and TIE-LO cells as they are logically equal .

Regards

Amrit

diablo over 13 years ago

No. VDD/VSS if tied directly to gate of NMOS/PMOS, noise in the power supply may turn on the gate. This effect is mitigated by using special cells like TIEHI and TIELO that prevent the MOS from inadvertently turning on with power/ground bounce.
Cancel
Vote Up 0 Vote Down

Cancel
tstark over 13 years ago

Don't some vendors allow direct VDD/VSS connections?
I'm not a layout guy, so I'm not sure how this is handled electrically (diodes, caps, etc.) but I've seen it before. Maybe some vendors allow but risk the noise issue?

tstark
Cancel
Vote Up 0 Vote Down

Cancel
vedamrit over 13 years ago

Whether this is appicable for 90nm and 130 nm also or we are using its for 65, 45 or 28nm only .
Cancel
Vote Up 0 Vote Down

Cancel
selvam27 over 13 years ago

I tried this in 45nm and 130 nm ,direct connections of VDD/VSS instead of TIE-HI/TIE-LO is supported and it does't create any lvs issues
Cancel
Vote Up 0 Vote Down

Cancel
Amare over 13 years ago

We ever had this kind of direct connection in our 0.18um chips.
Cancel
Vote Up 0 Vote Down

Cancel
Ganga111AtFPS over 13 years ago

Hi diablo,
How to make a TIE-HI or TIE-LO cells to drive constant 1-logic or constant 0-logic electrically?
To what terminals we will connect VDD/VSS nets ?
Thanks
Gangadhar
Cancel
Vote Up 0 Vote Down

Cancel
diablo over 13 years ago

TIE-HI and TIE-lo cells are already tied to constant 1-logic and costant 0-logic respectively.
To connect gates that are driven to constant 1 or 0 to tie cells, in RTL compiler there is command
'insert_tiehilo_cells -hi TIEHI_A7TULL -lo TIELO_A7TULL -all -maxfanout 20 -verbose'
To have global net connectivity physically, in Encounter you will have to run
globalNetConnect VSS -type tielo -inst * -module {} -override -verbose
globalNetConnect VDD -type tiehi -inst * -module {} -override -verbose
Cancel
Vote Up 0 Vote Down

Cancel
Ganga111AtFPS over 13 years ago

Thank you..
Cancel
Vote Up 0 Vote Down

Cancel

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.